1. Field of the Invention
The field of the invention relates to internal combustion (IC) engines. More particularly, the invention relates to toroidal internal combustion engines.
2. Description of the Prior Art
The traditional reciprocating IC engine has been around for more than 100 years, yet its design has several inherent disadvantages. One major disadvantage is that the energy released by combustion is converted work via linearly moving pistons and is then converted to rotational work output when it is transmitted to the crankshaft. This transfer of work output from linear to rotational motion is inherently inefficient for several reasons. For one, the slider crank mechanism that receives the work output from the piston is not at an optimum position for producing high torque on the crankshaft when pressure in the combustion chamber peaks and, consequently, only a portion of the energy generated by the combustion process is transmitted to the crankshaft, with the rest being dissipated in side thrust resulting in frictional work. Piston rings are used to provide a seal between the pistons and the cylinder wall, and also absorb the side thrust of the pistons that results from the slider crank configuration. With this configuration, the scraping action of the piston assembly, i.e., piston and piston rings, along the cylinder wall accounts for 50-70% of the total friction losses of this engine design.
The poppet valves typically used in the reciprocating IC engine are also sources of energy loss for several reasons. First, they are subject to high friction, noise, and vibration, all of which dissipate energy. The typical valve configuration, in which both intake and exhaust valves are located in close proximity to each other in the cylinder head, is also a source of energy loss during valve overlap. During valve overlap, in which both valves are open at the same time for at least a portion of a stroke, some of the fresh charge being drawn into the cylinder escapes directly through the exhaust valve, thereby reducing the mass of fuel-air mixture entering the cylinder. The heat transfer from the exhaust gas to the incoming charge also contributes to the reduction in mass of fresh charge available for combustion.
Rotary or toroidal IC engine designs have been investigated in the past in an attempt to overcome some of the inherent shortcomings of the traditional reciprocating IC engine. Rotary engines include designs with reciprocating pistons within a rotating housing, such as the Selwood Orbital and Bradshaw Omega toroidal engines, as well as cat-and-mouse piston designs, such as the Tschudi and Kauertz engines, in which pistons travel with variable velocity in a circular path. Toroidal engines have some distinct advantages over the traditional reciprocating piston engine, such as excellent balance (Selwood and Bradshaw Omega), absence of valve mechanisms, small size, and high power-to-weight ratio. The Wankel engine, an eccentric, three-chamber rotary engine, has perhaps found the most success with its simple design and small size. Despite these advantages, problems of nonuniform heating, sealing, inertia effects, and/or lubrication have prevented these engines from taking hold in the market place. These and other rotary engines are described in: Chinitz: Walter; Rotary Engines, Scientific American, February 1999, pp. 90-99.
A number of toroidal engines of the prior art teach a toroidal construction in which a pair of rotors that operate in parallel, but spaced-apart planes are enclosed within a housing. Piston vanes are integrally formed or mounted on the rotors, with the faces of the vanes forming increasing or decreasing chambers as the rotors counter-rotate, i.e., rotate in opposite directions. Parmerlee (U.S. Pat. No. 3,702,746; 1972) discloses such a toroidal engine that is a free-piston gas generator. Intake and exhaust ports are provided in the wall of the housing, as are bypass recesses. Simultaneous combustion in two chambers, spaced 180 degrees apart, forces the vanes on each rotor that bound the combustion chamber to move apart, thereby causing the rotors to rotate and simultaneously increase the combustion and intake chambers and decrease the compression and exhaust chambers. Ports and/or bypass recesses are situated in the housing such that they are appropriately opened or closed by the side walls of the vanes as they rotate within the housing. Kim (U.S. Pat. No. 6,321,693; 2001) also discloses an internal combustion engine having a rotor-piston-housing configuration similar to that of Parmerlee. In the Kim engine, intake and exhaust valves are placed in close proximity to each other on the housing, spaced 90 degrees apart. These engines solve some of the inefficiencies and force-balance problems inherent in a linearly reciprocating piston engine design that converts work output to rotary motion, because combustion is simultaneously taking place at two places 180 degrees apart within a torus. However, due to the configuration and engine construction, the forces exerted on the rotors and, thus, the housing are very high and will necessarily require very high-performance seals, problems that the designs of these engines do not solve. None of the disclosures for the toroidal engines of the prior art addresses cooling techniques to prevent overheating, warping, or destruction of the engine during routine operation.
What is needed, therefore, is an IC engine that provides superior performance with greater efficiency and reduced emissions. What is further needed is such an engine that is lighter in weight, smaller in size, and has fewer moving parts. What is yet further needed is such an engine in which the mechanical forces are dynamically balanced and the thermal stresses evenly distributed. What is still yet further needed is such an engine with reduced loads and requirements on seals, lubrication, and cooling.